1. Field of Invention
The present invention relates to an adaptive two-stage voltage regulator and a method for adaptive two-stage voltage regulation; particularly, it relates to an adaptive two-stage voltage regulator and a relevant method capable of adaptively adjusting a middle voltage according to a relationship between an input voltage and an output voltage, for reducing power consumption.
2. Description of Related Art
Referring to FIG. 1, in certain applications, it is required to perform two-stage voltage regulation in a power converter, wherein an input voltage is first converted to a middle voltage Vm, and the middle voltage Vm is next converted to an output voltage Vout. More specifically, in such two-stage voltage regulation, a first stage voltage regulator 10 is provided for voltage conversion with high efficiency, and a second stage linear regulator 20 is provided for filtering the ripple noise in the middle voltage Vm. For example, when a load circuit is an Active-Matrix Organic LED (AMOLED), the two-stage voltage regulator may be required.
Taking the load circuit being AMOLED as an example, in one application, the required output voltage Vout is 4.6V, while the input voltage Vin is a battery voltage which may vary between 2.5-4.8V; the voltage regulator 10 is a boost converter. Referring to FIG. 2, since the input voltage Vin may be 4.8V, to ensure that the boost converter operates normally, the output voltage Vm of the voltage regulator 10 is set to be 4.9V (the output voltage of the boost regulator must be higher than its input voltage; if the voltage Vm is set to be equal to or lower than 4.8V, the boost converter can not operate when the input voltage Vin is 4.8V). Next, a linear regulator 20 converts the middle voltage Vm (4.9V) to the output voltage Vout (4.6V).
In the foregoing arrangement, as shown in the drawing, when the input voltage Vin is in the range of 2.5-4.6V, a voltage difference ΔV of 0.3V (4.9V-4.6V=0.3V) is generated, which increases the power consumption of the circuit.
In view of the drawback of the foregoing prior art, the present invention provides an adaptive two-stage voltage regulator and a method for adaptive two-stage voltage regulation to reduce power consumption.